1. Field of the Invention
The present invention relates to a method for transmitting a short scheduling signaling through the padding bits in a Mac-e PDU in a WCDMA system that supports EUDCH.
2. Description of the Related Art
Standardization is to constitute the high rate and high quality packet service in the 3G mobile communication system. For instance, 3GPP is conducting standardization to HSDPA (High Speed Downlink packet Access) in order to improve the downlink data rate and 3GPP2 is conducting standardization to 1xEV-DV (Evolution-Data and Voice). 3GPP also goes on to an enhanced uplink data channel (EUDCH) in order to improve the volume and coverage of uplink. Compared with the uplink DCH of Re199/4/5, the EUDCH is superior in that a mechanism of HARQ (Hybrid Automatic Retransmission Request) is introduced in and the TTI (e.g., 2ms, the same as that of HSDPA) shorter than that of the uplink DCH of Re199/4/5 is considered for. TTI is defined as a transmission time interval to transmit data from a transmission channel to a physical channel.
The data transmission process in EUDCH is illustrated in FIG. 1. Whether to retransmit EUDCH data or not is under the control of the base station (hereinafter simplified as Node B).
When receiving the data from the UE and in case that the received data can be decoded correctly, Node B sends a correct acknowledgement (hereinafter simplified as ACK) to the UE indicating that data has been received correctly and new data may be transmitted in the next same process. The correctly received data is transmitted to a RNC, and the data is sorted by the RNC. If the received data may not be decoded correctly, Node B sends a NAK to the UE indicating that the data should be retransmitted in the next same process. Node B combines the retransmitted data with the just previous data received. Now, if the decoding may be conducted correctly, Node B transmits the correctly decoded data to the RNC.
Node B may schedule an absolute transmission rate of the UE in uplink. By sending an absolute scheduling command to the UE, Node B sets the transmission power of the UE, which is converted into the transmission rate. In addition, Node B also may perform relative scheduling to the rate that is being in service for the UE by sending the relative scheduling command to the UE to make it improve or reduce its transmission power or rate in current uplink by a preset step.
For the convenience of scheduling performed by Node B to the UE, it is necessary for the UE to inform Node B of some information. By far, two solutions may be adopted by the UE to inform Node B of some information. One is that the UE informs Node B of the information on the margin of power and the state of buffer area through a Media Access Control packet data unit (hereinafter MAC-e PDU). The packet containing the information on the margin of power and the state of buffer area is called a control packet, which is generally transmitted periodically. The other is that the UE sends the Rate Request message (hereinafter RR) to Node B via the channel of a physical layer, indicating whether the UE should improve its rate or reduce its rate and it is necessary to transmit RR in every TTI.
For the UE side in the EUDCH, a new MAC name MAC-e/es is introduced in. FIG. 2 shows a structure of MAC-e/es of the UE side. After a TFC (Transport Format Combination) is selected, signaling related to scheduling needs to be generated. The present invention relates to the range before that the UE transmits the MAC-e/es packet to the physical layer after the TFC is well selected. The MAC-e/es packet transmitted to the physical layer is just a MAC-e PDU (Packet Data Unit). The length of the MAC-e PDU must meet the demand of a set of predefined TFC. A proper format for transmission is selected for the UE MAC layer according to the number of data bits and the power needed to be transmitted. If the number of data bits needed to be transmitted is less than that required in the format, it is necessary to add some padding bits. At present, all padding bits are padded with zeros. Because the state of the buffer area and the margin of power occupy many bits, the control packet containing the information on the state of the buffer area and the margin of power is called a long control packet hereinafter. FIG. 3 illustrates a format of the MAC-e PDU, including a header and a payload. The payload includes data bits and padding bits.
In the state of SHO (Soft Switching Over), the Node B that may send the absolute scheduling command is a service Node B of the UE, which determines the required uplink rate for users according to the power of UE and the volume of data needed to be transmitted. The service Node B may not only send the absolute scheduling signaling to control the maximum transmission rate of the UE, but also send the relative scheduling signaling to the UE to improve or reduce its transmission rate with a preset step. To make the service Node B learn about the transmission power margin of the UE and the data size in the buffer area, it is necessary for the UE to transmit a long control packet to the service Node B. If the service Node B does not receive this long control packet, the UE should retransmit it. The non-service Node B sends common signaling to inform the UEs of the other cells whether they should reduce their rates or not, and the service Node B does not mind whether it has received the long control packet or not regardless the improvement in rate of the UE.
Because the physical channel resource is limited, only the most important information may be transmitted through it. At present, since other more important information should be transmitted through the physical channel, RR may be impossible to be transmitted through it. Therefore, the service Node B may perform scheduling according to the information on power and buffer reported by other UEs without the transmission of RR. However some limitation lies in this solution in the case that the UE makes a report periodically. Great changes have possibly taken place to the buffer area of the UE between the periods of two cycles. Therefore, the scheduling performed by Node B to the UE refers to earlier and inaccurate information thus it is possible that the resource allocated to the UE could not meet the demand of the UE.